Granite, marble, slate, ceramic, brick, and porcelain surfaces represent a large amount of floor and wall area in both residential and commercial buildings, with over 2 billion square feet installed in the United States each year. These products are often selected for use in areas which will see exposure to liquid water on a regular basis, such as in kitchens, baths, and exterior structures. Almost without exception, these surfaces are installed by adhering pre-cut tiles or stones to a wall or floor, with the spacing between the pieces subsequently filled with a cementitious matrix, commonly known as mortar or grout. Depending on the material, the tiles or stones themselves exhibit varying degrees of water porosity, ranging from relatively impervious in the case of porcelain tile to extremely porous in the case of marble. Regardless, almost without exception the grouting material is highly porous to liquid water.
Granite, marble, slate, sandstone, limestone, and other materials can generally be regarded as stones. These materials are mined, cut to a desired shape, and optionally may be polished or tumbled to achieve a specific surface appearance. Ceramics, porcelain, and bricks can generally be regarded as ceramic compositions formed by combining powdered precursors in specific ratios followed by heating to high temperatures to fuse the component grains together and form a final shape. Grout, mortar, cement, and concrete can generally be regarded as cementitious materials formed by combining powdered precursors with other additives (such as sand, gravel, etc.) and water. On contact with water, chemical reactions occur to cause the overall composition to harden, or cure, into a final composition.
Cementitious materials themselves may be characterized as hydraulic or non-hydraulic. Hydraulic cements are able to withstand immersion in water without short-term loss of strength. Examples of hydraulic cements include Portland and Rosendale cements. Non-hydraulic cements must remain dry to retain their strength. Examples of non-hydraulic cements include gypsum and Plaster of Paris.
In addition to use in conjunction with ceramic and stone surfaces, cementitious materials, especially hydraulic cements, are widely used in structural applications, including roads, bridges, foundations, and buildings. In these applications, concrete (a composite of cement and aggregate) is a dominant material. In many of these applications exposure to liquid water is both frequent and undesirable, due to the impact on the structural strength of the cementitious material itself and on reinforcing additives, especially steel.
As a consequence of the porous nature of these products and the environments they are installed in, liquid water often penetrates beneath the surface of these materials. Such liquid penetration is highly undesirable, since in the enclosed spaces rot, mildew growth, and degradation of the supporting substrates can occur. In addition, cementitious and other relatively porous materials can retain sufficient moisture such that they promote mold growth. In order to address this problem, a number of products have been developed. These products typically consist of an organic or semi-aqueous dispersion of a silicone or fluoroacrylic copolymer, which are applied after construction is complete, and on evaporation of the solvent deposits a water repellent polymer film on the tile and cementitious surfaces.
While these products exhibit varying degrees of efficacy in this function, they all possess a number of drawbacks. These include: the use of organic solvents or co-solvents, the need for a contiguous film after application, and the relatively non-specific nature of adhesion of the coating material. Thus, the use of organic solvents or co-solvents increases the difficulty and health risk associated with application of these products. The need for a contiguous film means water penetration can occur if there are breaks in the film surface. These breaks can occur due to incomplete application or due to abrasion and wear/tear on the surface film over time. The relatively non-specific nature of the adhesion means that considerable care must be taken during application in order to keep the coating material off of untargeted surfaces. Finally, because these products deposit a polymeric film, the thickness of the film is a function of the application process. Insufficient application will result in films that are too thin and/or non-contiguous, while excessive application will result in films that are greater than the desired thickness. Such thick films often exhibit haze, surface mottling, and other cosmetically unattractive features.